For the O2 period the influnce of altered maternal nutrition and maternal diabetes were examined on newborn lung. Newborn lungs from diabetic mothers showed increased CDP choline pathway activity, but a significant decrease in disaturated phosphatidylcholine. Fetal rat lungs (21 days) from mothers starved 4 days prior to term showed depressed (2-3H glycerol) incorporation via sn-glycerol-3-phosphate into phospholipids. Fetal lungs (21 days) from mothers fed a low protein diet (8%) showed decreased fetal weight, lung weight and a decreased phospholipid content. These data show that maternal alterations, induced in the in vivo metabolism, by dietary and hormonal states, markedly affect lung development.